Railway signaling.



W. F. FOLLBTT.

RAILWAY SIGNALING.

APPLICATION FILED NOV. 12, 1912- 1,1 17,559, Patented Nov. 17, 191i 2SHEBTSBHEET 1.

wlTNE/sjs j/ INVENTOR THE NORRIS PETERS c0. PHO10-LlTHf7.. WASHINGTON.n. C,

W. F. POLLETT RAILWAY SIGNALING.

APPLICATION nun NOV. 12, 1912.

1, 1 17,559. Patented Nov. 17,1914.

2 SHEETS'SHEET 2.

WW WaZaLa-WkTa-M THE NORRIS PETERS CO.PHOTOL!1HU,WA5HING You. 11 v.

TE STATES PATENT OFFICE.

WALDO F. FOLLETT, OF NEW HAVEN, CONNECTICUT, ASSIGNOR TO THE UNIONSWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OFPENN- SYLVANIA.

RAILWAY SIGNALING.

Specification of Letters Patent.

Patented Nov. 17, 1914.

To all whom it may concern:

Be it known that I, /VALDo F. FoLLn'r'r, a citizen of the United States,residing at New Haven, in the county of New Haven and State ofConnecticut, have invented certain new and useful Improvements inRailway Signaling, of which the following is a specification.

My invention relates to railway slgnalmg systems.

I will describe one form of railway signaling system embodying myinvention and will then point out the novel features thereof in claims.

In the accompanying drawings Figure 1. is a diagrammatic view showingone fornrof railway signaling system embodying my nvention, and Fig. 2is a view showing diagrammatically that the common wire for each blocksection is electrically disconnected from the common wire for eachadjacent block section.

Referring to the drawing, 1, 2, 3 and l designate four parallel tracksof a railway, here shown as being an electric railway. It is understoodthat the railway is provided with a suitable source of propulsioncurrent and with a third rail or trolley wire, but for the sake ofsimplicity these parts are omitted from the drawing. The track rails oieach track are divided into block sections L, K and N by any suitablemeans; as here shown these block sections are formed by insulated joints66 in both track rails of each track. Since the railway is an electricrailway, the track rails are preferably included in the circuit for thepropulsion current. I provide inductive bonds 55 by means of which thepropulsion current is conducted around the insulated joints 66 from thetrack rails of one block section to the track rails of the adjacentblock sections.

Traiiic along the tracks 1, 2, 3 and 4: is normally in the directionindicated by the arrows in these tracks. Traffic through blocksection Kover tracks 1 and 3 is governed by signals S and S; trailic throughblock section K over tracks 2 and i is governed by signals S and Ssimilarly trafiic over tracks 1 and 3 through block section L isgoverned by signals S and S and traffic over tracks 2 and 4 throughblock section l is governed by signals S and S Each of these signals isadapted to give three indications, namely, danger, caution and clear ashere shown, each signal compriscs two arms, a home arm it and a distantarm (Z, although I do not wish to be limited to this particular type ofsignal. It is understood that one arm three-position signals may equallywell be employed. It is also understood that regardless of the type ofsignal employed, each signal is provided with two controlling circuits,viz., a caution indication circuit and a clear indication circuit. Inthe case of two-arm two-position signals as shown in the drawing, thecantion indication circuit controls the controlling apparatus for thehome arm 72,, and the clear indication circuit controls the controllingapparatus :t'or the distant arm (Z.

Alternating signaling current for the signaling system is supplied bypower mains M extending along the trackway, which mains are suppliedfrom a suitable source, such as a generator 77. The signaling currentshould differ in character from the propulsion current; if thepropulsion current is alternating, then the signaling current difi'erstherefrom preferably in tli'requency. In the present case I will assumethat the propulsion current is 25 cycle current and that the signalingcurrent is (30 cycle current.

Located adjacent each set of signals is a transformer T or T, whoseprimary is connected with the power mains M and whose secondary isconnected with local distributing wires X and Y or X and Y.

Each block section of each track is provided with a track circuitcomprising as usual a source of current connected with the track railsadjacent one end of the block section and a track relay connected withthe track rails adjacent the other end of the For example, the source ofblock section. current for the track circuit for block section K oftrack 3 is a transformer 56 whose primary is connected with wires Xand Yand whose secondary is connected with the track rails by wires 58 and5%.). The track relay R" of this track circuit is as here shown of apolyphase type comprising one winding IV connected with the track railsby wires 60 and 61 and another winding V track winding to close itscontacts. Several types of relay of this character are known in the artand no further explanation is required. The sources of current for blocksections K of tracks 1, 2 and 4: are respectively transformers 57, 64and 65, andithe track relays for these track circuits are re spectivelyrelays R, R and B, each of which relays may be similar to relay R Forthe control of each signal I provide a signal relay. Signal S iscontrolled by relay B, signal S by relay D, signal S by relay F andsignal S by relay H. Each of these signal relays is of a 3-position typeand as here shown is of a single phase type comprising two members, anarmature a and a field winding f. Each of these relays is so arrangedthat when the armature a is in one extreme position the contact fingersengage the upper contact points; when the armature is in the otherextreme position, the contact fingers engage the lower contact pointsand when the armature occupies the middle position all the contacts areopen. The circuit for home arm h of each signal is controlled by theupper contact fingers 67 and 68 of the corresponding relay, and thecircuit for distant arm (Z is controlled by the two lower contactfingers 69 and 70 For example, the circuit for the home arm 71 of signalS is from wire Y through wire 13, upper or lower point of contact 67,wire 14., controlling apparatus for home arm h,

wire 15, upper or lower point of contact 68,

wire 16 to wire X. The circuit for the di tant arm (Z of signal S isfrom wire Y through wire 13, upper point of contact 69, wire 17,controlling apparatus for arm (Z, wire 18, upper point of contact 70,wire 16 to wire K. It will be seen therefore that when the ari'nature aof relay B occupies its m ddle position the circuits for both arms of sgnal are open so that the signal then in d cates danger; when. thearmature a occu pies its lower position so that the lower points areengaged by the contact fingers, the circuit for home arm h is closed andthe circuit for the distant arm (Z is open so that the signal thenindicates caution; but when armature a occupies its other extremeposition so that the upper points of the relay are engaged by thecontact fingers, the circuits for both arms are closed so that thesignal then indicates clear. The circuits for each of the signals S, Sand S are similar. to those just traced for signal 53 hence they neednot be traced herein. The field wind ing f of each signal relay isconnected with wires K, Y, or X, Y. For example the field winding 7'' ofrelay B is connected with wires X, Y, by. wires 78 and 79. The armaturewinding (4 of each signal relay is connected with a line circuitextending through the block section K and energized from the source ofsignaling current at the opposite end of the block section. Each ofthese line circuits is provided with a pole changer P, P, P or Prespectively, for reversing the polarity of the current in the linecircuit, these pole changers being operatively connected respectivelywith the home arm A, of signals S S S3 and S Each line circuit alsoincludes a transformer A, C, E or Each line circuit comprises a linewire individual to that circuit and a common wire 7, which common wireis common to all of the line circuits for block section K and is notconnected with the common wire of either of the adjacent block sectionsL or N. The fact that the common wire 7 of each block section iselectrically disconnected from the corresponding wire of each adj acentblock section is indicated in Fig. 2. The line circuit for relay Bincludes polechanger P and transformer A. The circuit of the primary ofthis transformer is as followsfrom wire Y through wire 51, contact ofpole changer P wire 52, primary of transformer A, wire 53, contact ofpole changer P wire 54, to wire X; the secondarycircuitfor this linecircuit is from the secondary of transformer A throughwires 5 and 6,common wire 7, wires 8 and 9, contact of track relay R wire 10, armaturea of relay B, wire 11, contact of relay R wire 12 to the secondary oftransformer A. The line circuit for relay 1) is similar to that justtraced for relay B and includes pole changer P, transformer C, linewires 27 and 7, and the contacts of track relay Bi. Similarly the linecircuit for relay F includes pole changer P transformer E, line wires4:7, and 7 and the contacts of track relay The line circuit for relay Hsimilarly includes pole changer P transformer G, line wires 38 and 7,and the contacts of track relay R The operation of the system may besufficiently explained by explaining the eifect on the circuits andapparatus of the passage of a car or train along track 3. WVhen theblock sections L and K of track 3 are unoccupied, as shown in thedrawing, track relay R5 is closed thereby holding closed the linecircuit for signal relay B. Home .arm h of signal S is in the inclinedposition so that pole changer l? is in such position that the polarityof the current in the line circuit for relay B causes the upper pointsof this relay to be engaged by the contact fingers so that signal Sindicate clear. If now, a car or train enters block section K from blocksection N it deenergizes track relay R thereby opening the line circuitfor relay B the armature of which then moves to its middle position;this opens the circuits for both the home and distant arms of signal Sso that this signal changes to danger indication. As the car or trainpasses out of block section K into block section L it similarly causessignal S to change to danger indication whereby reversing pole changer PTrack relay R now closes thereby closing the line circuit for signalrelay B but the polarity of the current in this line circuit having beenreversed by pole changer P, this relay is energized in such directionthat its lower points are engaged by the contact fingers thereby closingthe circuit for home arm h of signal S, but holding open the circuit forthe distant arm d of this signal so that signal S then indicatescaution. As the car or train passes out of block section L it causessignal S to change to caution indication, thereby again reversing polechanger P, so that the polarity of the current in the line circuit forsignal relay B is then such as to cause the upper points of this relayto be closed thereby causing signal S to again indicate clear. Theoperation of the apparatus foreach of the other three tracks is the sameas that which I have just explained for track 3, hence no furtherexplanation is necessary.

The circuits which I have hereinbefore explained are so arranged that afalse clear signal indication cannot be caused by broken wires, crossesor electromagnetic or static induction. I will now describe the effecton the system of these abnormal conditions. If any one of the line wires12, 27, 47 or 38 should become open, the 3-position signal relaycontrolled by such wire will be deenergized so that its contacts willassume their middle position, thereby causing the signal controlled bythat relay to indicate danger. If the common wire 7 becomes open theeflect is as followsif block sections K and L of track 3 are unoccupied,current will pass from the secondary of transformer A, through wires 5and 6, wire 34 to the point where it divides into wires 35 and .44,through wires 35 and 44 in multiple, contacts of relays R and R wires 36and 45 in multiple, armatures of signal relays H and F in multiple,wires 37 and 46 in multiple, contacts of track relays R and R inmultiple, wires 38 and 47 in multiple to secondaries of transformers Gand E, wires 32 and 43 in multiple, wire 33, wire 8 to point where itdivides into wires 9 and 24, thence through wire 9, contact of relay Rwire 10, armature of relay B, wire 11, contact of relay R wire 12 tosecondary of transformer A. i It will be seen, therefore, that if commonwire 7 is open and block sections K and L of track 3 are unoccupied,current from transformer A still passes through armature of relay B inthe normal direction so that this relay is still energized to causesignal S to indicate clear. Current from the secondary of transformer Cpasses through wire 23, then it flows in common with current fromtransformer A through wires 6 and 34, wires 35 and 44 in multiple,

contacts of relays R and R in multiple, wires 36 and 45 in multiple,armatures of signal relays H and F in multiple, wires 37 and 46 inmutliple, contacts of relays R and R in multiple, wires 38 and 47 inmultiple, secondaries of transformers G and E in multiple, wires 33 and8; from thence the current from transformer C alone passes through wire24, contact of relay R, wire 25, armature of relay D, wire 26, contactof relay R, wire 27 to secondary of transformer C. It will be seen,therefore, that current from transformer C still passes through signalrelay D in the normal direction so that this relay is still energizedtocause signal S to indicate clear. Current from transformer A cannotenergize relay D because wire 27 leading from that relay does notconnect with transformer A; and similarly current from transformer Ccannot energize relay B because wire 12 leading from that relay does notconnect with transformer C. Hence, when common Wire 7 is open and blocksections K and L of tracks 3 and l are unoccupied, the signals are notaffected.

If, while common wire 7 is open, a train enters either track 3 or 1 ofblock section K, signal S or S for that track will change to danger andthe other signal S or S will not be affected. lVhen such train passesfrom block section K into block section L,

the corresponding signal S or S changes to caution. For example, assumethat track 3 of block section L is occupied. The 130- larity oftransformer A is then reversed with respect to transformer C, andcurrent then flows from the secondary of transformer A through wire 12,contact of relay R wire 11, armature of relay B, wire 10, contact ofrelay R wires 9 and 24, contact of relay R, wire 25, armature of relayD, wire 26, contact of relay R, wire 27, secondary of transformer C,Wires 23 and 5 to secondary of transformer A. The direction of thiscurrent in relay B is such1as to energize that relay in such directionas to cause signal S to indicate caution, and the direction of thiscurrent in relay D is such as to energize that relay in such directionas to cause signal S to indicate clear. Hence, the proper operation ofthese signals is not interfered with, and the opening of common wire 7cannot cause a false clear signal. The circuits for signal relays H andF from transformers G and E in case common wire 7 becomes open aresimilar to those just explained for signal relays B and D.

Assume that any one of the wires 12, 27, 47 or 38 becomes crossed withthe common wire 7, as for example, that line wire 12 be comes connectedwith common wire 7, as indicated at 71 on the drawing. Current will thenflow from the secondary of transformer A through wires 5, 6 and 7 to thecross 71,

at which point it. divides, part passing through wires 7, S and 9,contact of relay R wire 10, relay B, wire 11, contact of relay R, wire12 to the cross 71; thence through wire 12 to the secondary oftransformer A; the remainder of the current will flow from wire 7through the cross 71 to wire 12, thence through wire 12'to transformerA. If the cross 71 is of sufliciently low resistance such a largeportion of the current will pass through the cross that the signal relayB will be deenergized and signal S controlled thereby will indicatedanger. If however the cross 71 is not of sufliciently low resistance,the operation of the system will not be interfered with. A similarcondition would exist in case of a cross between common wire 7 and anyone of the remaining line wires.

Assume now that a cross exists between any two of the wires 12, 27, 17and 38, for example, between wire 12 and 27 as indicated at 72 on thedrawing. Current would then flow from the secondary of transformer Athrough wires 5, 6,7, 8 and 9, contacts of relay R wire 10, relay B,wire 11, contact of relay R wire 12, to the point of cross 72; iftransformer C is energized with the same polarity, current will flowfrom the sec ondary of this transformer through wires 23, 6, 7, 8 and24, contact of relay R, wire 25, relay D, wire 26, contact of relay R,wire 27 to the point of cross 72; these two currents at the point 72have the same polarity and the same potential, hence, they will flowthrough their respective wires 12 and 27 to the secondaries of theirrespective transformers A and C. Hence, when the transformers A and Chave the same polarity the cross 72 will have no effect on the,signaling system. Assume however, that the cross 72 exists and that thepolarity of the transformers A and C is opposite; for example, assumethat the polarity of transformer A remains as before but that thepolarity of transformer C is reversed by the presence of a car or trainin block section L of track 1. Then current attempts to flow ashereinbefore explained from transformer A through wires 5, 6, 7, etc.,to relay B and wire 12 to cross 72; at the same time current willattempt to flow from the secondary of transformer C through wire 27 tothe point 72. These two currents have opposite polarity at the point ofthe cross 72, so that the current from transformer A which was supposedto have passed through relay B is checked by the counter current throughwire 27, and it passes instead through wires 5 and 23 to the right handof the secondary of transformer C, through this secondary to wire 27 tocross connection 72, wire 12, back to the left hand side of thetransformer A, with the result that the two transformers A and G areshort circuited and practically no current passes through the signalrelays B or D; These relays are therefore deenergized causing signals Sand S to indicate danger. I

I will now describe the effect on the signaling system ofelectromagnetic induction from an adjacent alternating current powerline. Assume that such power line extends along the railway paralleltherewith and that it is carrying a heavy 25 cycle propulsion current.This current will create an induced voltage upon the line circuits ofthe signal system by electro-magnetic induction. The strength of theinduced voltage is dependent upon the strength of the propulsioncurrent, the distance between the propulsion lines and the signal lines,and the continuous length of the signal lines. In order to-break thecontinuity of the signal lines and thereby limit-the possible values ofthe induced voltage, the signal lines for each block section, includingthe common wire 7 are made electrically independent of the signal linesfor the adjacent block sections as hereinbefore explained. Assume thatthe. line circuits are sufficiently insulated from the ground towithstand this impressed voltage and also assume that at a given instantthe induced current in the line circuits is flowing in the directionindicated by the'arrow 73. This induced current has a tendency 'to flowthrough wire 12, contact of relay R wire 11 to armature aof relay B;simultaneously an equal induced current has atendency to flow throughwire 7 in the direction of the 311'. row 7 3,through wires 8 and9,contact of relay R wire 10 to the other terminal armature a of relayB. These two currents will neutralize at the armature of relay B, hence,no induced current would fiow through this armature, and the inducedcurrent would have no effect on the signaling system. A similarcondition would existas to the three remaining line circuits and signalrelays.

Assume that the conditions electrically are the same as just describedwith the exception that line wire 12 is grounded at the extreme ends ofthe block section, as for example, at the'points 74: and 7 5. VVhen thecurrent surge is in the direction indicated by arrow 7 3,,the inducedcurrent would neutralize as heretofore explained but there will beanother circuit established by the induced current as follows from wire12 to the ground at point 75, thence through the ground to pointv 74 andback to wire 12; also there will be a similar circuit established fromwire 7 through wiresv 8 and 9, contact of relay R wire 10, relay B, wire11, contact of relay R wire 12 tothe ground at point 75, thence throughthe ground to point 74, to wire 12, secondary of transformer A, wires 5and 6 to wire 7. Thus an induced current flows through the armature ofrelay B. When a car or train occupies block K of track 3, this currentwill not affect the relay B because the contacts of track relay R willbe open thus interrupting the circuit for the induced current justrecited. Assume now that with the conditions just described, blocksection K is free but that a car or train occupies block section L oftrack 8, thereby changing the polarity of the line circuit of signalrelay B; this would under normal conditions cause signal S to indicatecaution. Since the contacts of track relay R are now closed the inducedcurrent wouldnow pass through the armature of relay B as just explained.The conditions which now exist would be a (30 cycle signalingcurrent anda 25 cycle pro pulsion current in both the field and the armature ofrelay B, the 60 cycle signalin current being the normal energy suppliecfrom the signal system. The 25 cycle propulsion current would passthrough the armature of relay B, as cited above, and in passing throughtransformer A would cause 25 cycle energy in the power wires X and Y,which, in turn, would cause 25 cycle current in the tracks through thetrack transformers 5G and 57, and through'transformer T into the powermains M, thence through transformer T into wires X and Y, and thenceinto the field of relay B. The effect of this would be to reverse thetorque of the armature of relay B. At the same time, the 25 cycle energyin the frequency track relay would cause the contacts of the track relayto open, thus deenergizino relay B. The interrupting of the circuitthrough the armature of relay B would also interrupt the inducedcurrent, eliminating the effect of 25 cycle energy upon the instrumentsin question, and they would immediately assume their former position bythe 60 cycle energy present. lVith the establishment of the formerposition of the instruments, the 25 cycle circuit would bereestablished. Thus it will be seen that the contacts of relay B wouldvibrate between this former position and neutral position, thus causingthe signal S to give either the caution indication or danger indication.

At the instant when the direction of the surge of induced current in theline wires is as indicated by arrow 76, the effect on the signalingsystem would be the same as hereinbefore described, except that thedirection of the flow of the current would be reversed at the same giveninstant.

As for static induction the signal line wires would be continuouslycharged statically from the adjacent propulsion line up to a voltagedependent upon the voltage of such line and upon the break-downinsulation resistance of the line wires of the signaling system. By theintroduction of lightning arresters having a suitable predeterminedbreak-down resistance, which resistance is lower than the break-down resistance of the signal line wires, these line wires could be constantlydrained of the voltage impressed statically above the breakdown point ofthe arresters.

Although I have herein shown and described only one form ofsignalingsystem embodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is 1. In combination, ablock section of a railway track, a signal located adjacent the entranceend of the section and adapted to give three indications, power mainsextending through the section, a source of alter nating signalingcurrent for said power mains, a main transformer located adjacent eachend of the section, the primary of each main transformer being connectedwith said power mains, electromagnetic means for controlling said signaland comprising two windings one of which is constantly connected withthe secondary of the main transformer at the entrance end of thesection, a line circuit comprising two line wires connected with theother winding of said electromagnetic means and extending through thesection, a line transformer whose primary is connected with thesecondary of the main transformer at the exit end of the section andwhose secondary is connected with said line wires, means for reversingthe connection of the primary of the line transformer with the secondaryof the last-mentioned main transformer, said electromagnetic means beingresponsive to said reversals of connection, and a track circuit for thesection including a track relay for controlling said line circuit.

2. In combination, a railway comprising two parallel tracks over whichtraflic moves in the same direction, a block section for each track, asignal for each block section adapted to indicate danger, caution andclear, a three-position signal relay for the control of each signal, asource of alternating signaling current, a line circuit for each signalrelay each comprising a line wire individual to such circuit and acommonwire common to both circuits, a transformer for each line circuitwhose primary is connected with said source of signaling current andwhose secondary is connected with the line circuit, a pole-changer foreach line circuit for reversing the current in the line circuit withrespect to the source, and a track circuit for each block section eachincluding a track relay for controlling the line circuit of such blocksection.

3. In combination, a railway comprising two parallel tracks over whichtraflic moves in the same direction, a plurality of successive blocksections for each track, the block sections of each track beingsubstantially oppositely located, signals for the block sections adaptedto indicate danger, caution and clear, a three-position signal relay forthe control of each signal, a source of alternating signalingcurrent, aline circuit for each signal relay each line circuit comprising a linewire individual to such circuit and a common wire common to the linecircuit of the oppositely located block section of the other track, atransformer for each line circuit whose primary is energized from saidsource of signaling current and whose secondary is connected with theline circuit, means controlled by each signal for reversing the currentin the line circuit for the block section in the rear relative to thesaid source, and a track circuitfor each block section each including atrack relay for controlling the line circuit of such block section.

4. In combination, a railway comprising a plurality of parallel tracks,a block section for each track, a signal for each block section adaptedto give three indications, a three-position signal relay for each signalfor the control thereof, a source of alternating signaling current, aline circuit for each signal relay each comprising a line wireindividual to such circuit and a common wire common to all of the linecircuits, a transformer for each line circuit whose primary is connectedwith said source of signaling current and whose secondary is connectedwith the line circuit, a pole changer for each line circuit forreversing the current in the line circuit with respect to the source,and a track circuit for each block section each including a track relayfor controlling the line circuit of such block section.

5. In combination, a railway comprising a plurality of parallel tracks,each track being divided into a plurality of successive block sectionsand the block sections of each track being substantially opposite thoseof the other track or tracks, signals for the block sections adapted toindicate danger, caution and clear; a three-position signal relay forthe control of each signal, a line circuit for each signal relayextending through the block section, a source of altertrack rails ofeach block section for controlling the line circuit of the blocksection.

6. in combination, a railway comprising a plurality of parallel tracks,each track being divided into a plurality of successive block sectionsand the block sections of each track bein substantially opposite thoseof the other track or tracks, signals for the sections, a line circuitfor each block section of each track extending through the blocksection, each line circuit comprising a line wire individual to thecircuit and another line wire common to the line circuits of theopposite block sections, said commonwire for each set of block sectionsbeing electrically insulated from the common wires'for the adjacent setsof block sections, means controlled by each line circuit for controllingthe signal for the corresponding block section, and a track relayconnected with the track rails of each block section for alsocontrolling the signal for the block section.

7. In combination, a railway comprising a plurality of parallel tracks,each track being divided into a plurality of successive block sectionsand the block sections of each track being substantially opposite thoseof the other traclr or tracks, signals for the sections, a line circuitfor each block section for the control of the signal for such section,each line circuit extending through the section and comprising a linewireindividual to the circuit and another line wire common to the linecircuitsof the opposite block sections, the said common wire for eachset of oppositely located block sections being electrically insulatedfrom the common wires for the adjacent sets of block sections. 7

8. In combination, a railway comprising a plurality of-parallel tracks,each track being divided into a plurality of successive block sectionsand the block sections of each track being substantially opposite thoseof the other track or tracks, signals for the sections, a line circuitfor each block section for the control of the signal for such section,each line circuit extending through the section the line circuits foreach set of oppositely located block sections being electricallyinsulated from the line circuits for the adjacent sets of blocksections.

9. In combination, a railway comprising two tracks over which traflicmovesin the same direction, a block section for each track, a signal foreach block section and adapted to give three indications,electromagnetic means for each signal for the control thereof, a sourceof alternating signaling current, a line circuit for the electromagneticmeans for each signal, each line circuit comprising a line wireindividual to the circuit and a common wire common to both circuits, atransformer for each line circuit whose primary is connected with saidsource and whose secondary is connected with the common wire and withthe line wire individual to the circuit, a pole-changer for each linecircuit for reversing the connection of the primary of the corresponding transformer thereofwith the source, each electromagnetic means belngresponsive to such reversals, and a track circuit for each block sectionincluding a track relay 10 for controlling the line circuit for thesection.

In testimony whereof I afiix my signature in presence of two witnesses.

WALDO F. FOLLETT. Witnesses:

GEORGE Lnn'rn PEGK, ELMER B. MYERS.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, I). O."

